Diaphragm for sound-reproducing instruments



May 6 1924. 1,492,982

G. F. c. HOUGHTON DIAPHRAGM FOR SOUND REPRODUCING INSTRUMENTS Filed Feb. 15. 1922 v ATTORNEY Patented May 6, 1924.

UNITED STATES 2, PATENT OFFICE.

GEORGE F. C. HOUGHTON. OF NEW YORK, N. Y., ASSIGNOR TO SYDNEY B. HOPKINS, OI SUMMIT, NEW JERSEY.

DIAPHRAGM FOR SQUND-REIPRODUCING INSTRUMENTS.

Application filed February 15, 1922. Serial No. 536,658.

To all whom it may concern:

Be it known that I. GEORGE F. C. HOUGH TON. a citizen of the United States, residing at New York, in the county and State of 5 New York, have made certain new and useful Improvements in Diaphragms Sound-Reproducing Instruments, of which the following is a specification.

The invention relates to novel and useful diaphragms for sound reproducing instruments and to a. novel and useful process for producing them. i

Objects and advantages of the invention will be set forth'in part hereinafter, and in part will be obvious herefrom or may be ascertained by practice with the invention.

The invention consists in the novel steps, processes, parts, articles, constructions and arrangements herein shown and described,

The accompanying drawings, referred to herein and constituting a part hereof, illustrate diagrammatically one embodiment of the invention, and together with the description, serve to explain the principles thereof.

Of the drawings:

Fig. 1 is an edge View of the blank;

Fig. 2 is an edge view of the compressed blank; and

Fig. 3 is a plan of the completed diaphragm.

It will be understood that the drawings are necessarily diagrammatic and while adequate to explain the invention do not necessarily represent the actual proportions and other relations of the parts of the diaphragm. 7

In the present preferred form of carrying out the invention, I employ as the basic element or component of the diaphragm a cellular and compressible material. and preferably a material of relatively light specific gravity, that is, of relatively low or, small density, and in certain as ects of the inven-- tion'I preferably employ alsa wood. This exceedingly light and relatively highly compressible and. without pronounced contrasts of fibrous structure, while having the requisite cellular structure.

The balsa wood or other equivalent material'is impregnated with a medium which renders it homogeneous, imparts uniformity thereto as. to relative rigidity and flexibility, and renders it immune to tem )erature and for have some part wood is of relatively uniform structure, is'

atmospheric changes, and also imparts to it uniform acoustic properties, that is, renders. it uniformly sensitive to acoustic action except as intentionally modified by the shape and dimension of the diaphragm.

According to my preferred present practice, the balsa wood or equivalent material is formed into blanks 1, preferably rectangular and of suitable size and thickness. I make the blanks at present about 35/1000 of an inch thick, but I do not wish the invention to be in anywise so limited. These blanks are immersed in a solution of formaldehyde and carbolic acid in liquid form, this mixture being known commercially as bakelite or condensite. The immersion is continued untilthe wood is completely impregnated with the liquid, after which the blanks are dried out to removethe surplus liquid therefrom, but leaving the structure of the wood impregnated therewith. That is. the blanks are dried out in the atmosphere to remove the surplus liquid just sufficiently so that the blanks may be handled in the further process without difliculty.

There is then applied to the outer surface on the blanks a protective layer, which may ikewise in the reproducing operation. In the present preferred practice, I apply a layer of paper to either side of the blank. For this pur ose an adhesive .is applied thereto, and pre erabl I employ a cellulose mixture of rather ieavy consistency, known as "aeroplane'dope, and coat both sides of the blank therewith, and this is preferably sprayed on the blanks-tqse cure aneven application thereof, and thi coating is allowed to dry.

The blank is then preferably dipped in acetone or banana oil and the paper is then laid on and pressed into place and the blanks are dried, as shown at 2 and 3.-

The blanks are then put in the press and are subjected to rather high heat, butare ke t well'below the charring or combustion, point under these conditions. I prefer at presents temperature of about 200 degrees phragm and is concentriotherewith. 11.

In the pressing operation, a layer of fabric, of coarse weave, is preferably interposed between the blank and the die, and the best results are effected by having this on both sides of the blank. This imparts under the heat and heavy pressure a structure or .conformationito the blank, slightly corrugated or roughened which renders it more sensitive to the mechanical vibrations from the record, and also in like manner more efiicient in creating or reproducing the duplicate sound waves. The cloth or fabric also assists in stripping the blanks from the dies.

It will be understood that departures may be made from the exact manner of carrying out the invention herein shown and described, within the scope of the accompanying claims, without departing from the principles of the invention and without sacrificin its chief advantages.

W at I claim is l 1. A sound reproducing diaphragm, comprising a layer of balsa wood.

2. 'A sound reproducing diaphragm, comprising a layer of balsa wood impregnated with bakelite.

- surface.

5. A sound reproducing diaphra m, com prising balsawood impregnated with bakelite, protective layers on opposite sides thereof, the diaphragm having corrugations pressed into it on its exterior surface.

6. The process of making sound reproducing a disk of cellular material with bakeliteforming liquid, applying adhesive to opposite sides thereof, applying protecting layers on said adhesive, and subjecting the assem bly to high pressure at an elevated temperature for forming solid bakelite, for softening the adhesive and coalescing the disk and protecting layers into a unitary diaphragm.

8. The process of making sound reproducing diaphragms, comprising impregnating'a disk of balsa wood with bakelite, applying adhesive to opposite sides thereof, applying protecting layers on said adhesive, and subjecting the assembly to high pressure at an elevated temperature.

9. The process of making sound reproducing diaphragms, comprising impregnating balsa wood with bakelite, then heating and compressing it and simultaneously forming corrugations in its surface.

10. The process of making sound reproducing diaphragms, comprising impregnating balsa wood with bakelite and compressing and heatin the blankin contact with a layer of fabric.

In testimony whereof, I have signed my name to this specification.

GEORGE F. o. HOUGHTON. 

